1. Field of the invention
The present invention relates to a rotation detecting device of an automatic transmission, in detail, it relates to a rotation detecting device of an automatic transmission, having a rotation detecting sensor to detect a number of rotation of a rotating shaft supported inside a case.
2. Description of the prior art
Generally an automatic transmission has rotating members such as an input shaft, an output shaft and the like. It also has a rotation detecting means to detect a number of rotation of the rotating member for the purpose of controlling, for example, a lock-up clutch and the like. Conventionally rotation detecting means 3 such as a sensor and the like is, as shown in FIG. 4 (a), (b) and FIG.5 (a), (b), situated at the outside or the inside of a rotating member 10, and detects a number of rotation of the rotating member 10. However, the rotation detecting sensor requires a mounting space axially and radially. In a case of detecting the number of rotation of rotating members such as an input shaft and the like which is installed in the center (deep inside) of the automatic transmission, the above rotation detecting sensor must be situated near the back end of the input shaft or on the surface of the case so as to detect a the rotation of a flange member fixed radially on the input shaft. When placing the sensor to the side of the input shaft, the axial length of the transaxle case increases, while when placing it on the surface of the case, the radial length of the case increases, so that such increase of size in both axial and radial direction can not cope with the recent tendency for the automatic transmission (designed for the front-engine-front-drive cars), which requires further narrower mounting space.